It’s a vow that holds a very different meaning for Tiffany Au and Caleb Remington as they prepare to say “I do” this spring.

Neither knows how many days they will have together as a married couple, but they’re used to facing what many perceive to be unbeatable odds.

Remington has spent his life battling cystic fibrosis, a genetic and life-threatening disease that affects the lungs and digestive system.

“We are constantly battling infections and bacterial infections, viruses. I personally take over 60 pills and have to do breathing treatments for 2 hours a day." Remington said. “The life expectancy was only 19 years old [when I was diagnosed].”

Photo credit: Tiffany Au

Now 27, death has become an every day topic for Remington and his soon-to-be wife, an outwardly positive pair from Chicago’s suburbs.

“Where most people talk about what their favorite movies are or what they’re interested in or what they do in their leisure time, we were talking about the depths of life,” Remington said. “She not only gets it, but she can meet me with compassion and empathy.”

“I remember the first time we actually [talked about it]. ... He was asking me how many kids do you want?” Au said. "I responded at least three and he went silent after that.”

Remington now has a life expectancy of just 37, according to the medical encyclopedia, making each and every day a different challenge for him and his fiancée.

“Entering a relationship with someone who has a terminal illness – it is scary,” Au said. “But then I thought, it's far more worth it to spend 10 quality years filled with adventure, challenges and growth than 50 years of a stagnant flow. I was like, 'I'm taking the plunge.' It's worth it."

Though they have never been a “normal couple,” Remington and Au have decided to take their unique situation to new heights – using their wedding day as a call to action.

It’s an unconventional wedding for a couple facing an unconventional situation, and it brings an entirely new meaning to another vow they’re prepared to make on their big day.

“For richer or poorer.”

Unlike traditional weddings, there will be no wedding gifts, no money given to them as they start the next chapter of their life together– there will only be fundraising for charity.

They’re calling it the Greatest Wedding Ever Donated, or the GWED, planning to turn their wedding day into a fundraising gala and benefit concert that aims to raise $500,000 to be split evenly between five organizations.

Each organization serves a cause close to the couple’s hearts: mental health, rare disease, research, education and low-income families.

Rare disease and research apply largely to Remington’s disease, and mental health, education and low-income families play a large role for Au - a sexual assault survivor and educator who grew up in a low-income family.

“I wouldn’t be alive if it wasn’t for the community that has helped raised so much funds and awareness for cystic fibrosis and research,” Remington said.

“With our whole relationship community has been a center of focus,” Au said. “Community, for me, and community service is what saved my life.”

The idea to transform their wedding sprouted almost immediately after the two got engaged during a vacation to Hawaii last year.

“We knew we wanted to do something different,” Remington said.

Facing a grim clock on their life together, the pair hope to make the biggest impact possible with the time they have left.

“On a wedding day, people gather, everyone is there for you. So, you have everyone’s attention whether you want it or not for that day,” Au said. “So what are you going to do with that attention? Our minds are always like, ‘How can we use that to help other people?’”

Photo credit: Samantha Chou

Their wedding day, which will be in California, will feature a charity gala that will include a silent auction, a live auction and even a benefit concert that will be open to the general public - or what they have called "wedding crashers."

But for those who can’t attend the big day on May 5, there’s also a GoFundMe page looking to raise $50,000 of their $500,000 goal just before the Christmas holiday. They are also accepting donations via their website up until the big day.

“Every dollar counts,” Au said.

Remington and Au are prepared to spend $30,000 on the charitable festivities to allow for all money raised to go to the charities themselves, but they aren’t doing it alone.

The day-of videography and photography, table decorations, invitations and more have been donated for their day.

The Wayfarer Foundation, which was co-founded by Justin Baldoni of the award-winning Jane the Virgin TV show, has also signed on as a fiscal sponsor of the event. Having a fiscal sponsor also means all donations are tax deductible.

“[Tiffany and Caleb are] creating an entire platform to be of service for others through GWED,” said Ahmed Musiol, co-founder of the Wayfarer Foundation. “It’s an incredible way to lay the foundation for a marriage that will stand the test of time, God willing, because it isn’t about being self-serving. What they’ve created is in fact the macro version of marriage.”

And beyond raising money for charity, Remington and Au hope to make an even larger statement with their “wedding.”

“Our biggest dream with it is that we’re able to start this new kind of movement for couples to consider adding philanthropy to their big day, whether it be replacing their registry for charity or going on a mission trip for your honeymoon - it definitely doesn’t have to be this grand gesture,” Au said.